Recently, a spacer prepared from a photosensitive resin composition is employed in order to maintain a constant distance between the upper and lower transparent substrates in liquid crystal cells of a liquid crystal display (LCD). In an LCD, which is an electro-optical device driven by a voltage applied to a liquid crystal material injected into a constant gap between two transparent substrates, it is very critical to maintain the gap between the two substrates to be constant. If there is an area in which the gap between the transparent substrates is not constant, the voltage applied thereto as well as the transmittance of light penetrating this area may vary, resulting in a defect of spatially non-uniform luminance. According to a recent demand for large LCD panels, it is even more critical to maintain a constant gap between two transparent substrates in an LCD. Such a spacer may be prepared by coating a photosensitive resin composition onto a substrate and exposing the coated substrate to ultraviolet rays and so on with a mask placed thereon, followed by development thereof. Recently, efforts of using a light shielding material for a spacer have been made; accordingly, various colored photosensitive resin compositions have been actively developed.
In recent years, a black column spacer (BCS) in which a column spacer and a black matrix are integrated into a single module using a colored photosensitive resin composition has been aimed to simplify the process steps. The colored photosensitive resin composition used in the production of such a black column spacer is required not only to easily form a step difference but also to meet an elastic recovery rate at the same time to have resistance to the pressure of the upper plate. Furthermore, if a cured film has uneven wrinkles on its surface when a bezel is formed from a colored photosensitive resin composition in a display panel, it may cause a serious disadvantage that the amount of injected liquid crystals may not be uniform due to a defect in the gap between the upper and lower plates during their assembly or that spots may be generated on the display screen due to a poor transmission of electric signals.
In the meantime, in order to impart a high light shielding property to a black column spacer (BCS), the content of a pigment added to the resin composition must be increased. In this regard, Korean Patent No. 0814660 discloses a black photosensitive resin composition comprising a black organic pigment, which has a good light shielding property and a low dielectric constant. However, if a large amount of a black organic pigment is employed, the pigment is eluted inside the spacer due to an increase in the amount of the organic pigment that has insufficient chemical resistance. In addition, as the amount of the pigment increases in the photosensitive resin composition for forming a spacer, the amounts of a binder, a photopolymerizable compound, and the like are relatively reduced, which causes a problem that the elastic recovery rate of the spacer is lowered.